The present invention relates to systems for avoidance of hazards and collisions. More particularly, the present invention relates to a radio warning system that alerts vehicle operators and other persons carrying system receivers of hazardous conditions so that such conditions can be avoided.
Today, persons traveling from one location to another are being confronted with hazardous conditions with increasing frequency. Roads and highways have, for example, become more populated in recent years, presenting unsuspecting persons, such as pedestrians and operators of motor vehicles, with increased threats to their safety from approaching emergency vehicles, buses, trains, or the like. In many cases, such persons may not be aware of the impending threat, which creates a dangerous situation.
For instance, the passenger compartments of most automobiles are designed and manufactured such that outside noises cannot be heard when the windows of the compartment are closed. Operators and passengers of an automobile may, therefore, have difficulty hearing sirens, horns or whistles from other approaching emergency vehicles, buses or trains. Thus, when an ambulance or fire truck is responding to an emergency call, an unsuspecting motorist may never see or hear the rapidly approaching emergency vehicle and, consequently, may be unable to steer clear of the emergency vehicle's path. This creates a potential hazardous situation for the operators and passengers of the motor vehicle and emergency vehicle alike.
Similarly, a pedestrian or other person who may be traveling by foot, wheelchair, or bicycle, may also be presented with hazardous conditions, particularly where that person is physically-challenged from loss of hearing or sight. In such instances, these persons may likewise be unaware of an approaching emergency vehicle, bus or train simply because they cannot hear its siren, horn or whistle, or cannot otherwise see it as it approaches. Under these circumstances, such persons may be unable to stay out of harm's way, creating yet another hazardous and dangerous condition.
Prior art systems have, to a limited extent, recognized the need for warning automobile operators and others of approaching vehicles for purposes of collision avoidance. However, these systems have significant limitations and disadvantages. For example, radio frequency (RF) energy has been used, in prior art systems, to alert the occupants of one vehicle to the presence of another vehicle. In such systems, RF signals were transmitted from one vehicle and detected by a unsuspecting second vehicle. Upon detection, a warning signal was generated in the second vehicle. The warning signal, however, was transmitted over the radio or through independent audio and visual components, as shown in U.S. Pat. No. 3,854,119, issued to Friedman et al., and U.S. Pat. No. 3,876,940, issued to Wickford et al. The Friedman patent describes the use of amplitude modulated signals to operate switching means for activating devices such as audio speakers, light emitting diodes, panel displays or neon lights in relation to the amplitude of the received signals. The Friedman patent, however, requires constant transmission of amplitude modulated signals which do not perform well in the presence of interference or multipath distortion. The Wickford patent discloses a warning device utilizing radio transmission on an assigned frequency having a transmitter in the emergency vehicle and a receiver in the regular vehicle. The Wickford patent makes use of a receiver that mutes the broadcast reception on the vehicles radio or otherwise turns the vehicles radio on, and applies the warning signal through the vehicle's radio system. Such a system has not, however, become accepted in the marketplace because it is expensive, susceptible to "false triggers" (i.e., false alarms), and would require additional end-user licenses from the Federal Communications Commission (FCC) before the system could be operated in the general consumer broadcast (e.g., AM or FM) bands.
For these reasons, other prior art systems have abandoned RF signaling as a method for transmitting warning signals and, instead, have elected to use systems that require line of sight (LOS) communications and other communication systems that use receivers having a small beamwidth such as U.S. Pat. No. 5,314,037, issued to Shaw et al. and U.S. Pat. No. 5,495,243, issued to McKennan. However, these prior art systems have also not received acceptance in the marketplace, primarily because they are not effective unless the system's receiver is within the LOS or beamwidth of the system's transmitter.